The invention relates generally to battery electrolytes. More particularly, the invention relates to battery electrolytes to improve stability of batteries, such as one or more of high voltage stability, thermal stability, electrochemical stability, and chemical stability.
An electrolyte serves to transport ions and prevent electrical contact between electrodes in a battery. Organic carbonate-based electrolytes are most commonly used in lithium-ion (“Li-ion”) batteries, and, more recently, efforts have been made to develop new classes of electrolytes based on sulfones, silanes, and nitriles. Unfortunately, these conventional electrolytes typically cannot be operated at high voltages, since they are unstable above 4.5 V or other high voltages. At high voltages, conventional electrolytes can decompose by catalytic oxidation in the presence of cathode materials to produce undesirable products that affect both the performance and safety of a battery.
In the case of Li-ion batteries, cobalt and nickel-containing phosphates, fluorophosphates, fluorosulphates, spinels, and silicates have been reported to have higher energy densities than LiFePO4, LiMn2O4, and other commonly used cathode materials. However, these cathode materials also have redox potentials greater than 4.5 V, allowing for operation of the battery at higher voltages but also possibly causing severe electrolyte decomposition in the battery. In order to use a cathode material to deliver a higher energy density at a higher voltage platform, the hurdle of electrolyte decomposition should be addressed at least up to, or above, a redox potential of the cathode material.
Another problem with both organic carbonate-based electrolytes and other classes of electrolytes is chemical stability at elevated temperatures. Even at low voltages, elevated temperatures can cause conventional electrolytes to decompose by catalytic oxidation in the presence of cathode materials to produce undesirable products that affect both performance and safety of a battery.
It is against this background that a need arose to develop the electrolytes and related methods and systems described herein. Certain embodiments of the inventions disclosed herein address these and other challenges.